1. Field of the Invention
The present invention generally relates to an intersection warning system, and more particularly to an intersection warning system issuing a warning to a driver of a vehicle running near a roadside edge and approaching an intersection, based on a state of another vehicle running, near the roadside edge, in a sideward or rearward area of the vehicle.
2. Description of the Related Art
For example, in a case where every vehicle ought to run on a left side of a road, a driver of a vehicle running near the roadside edge and approaching an intersection to turn left at the intersection has to pay attention to another vehicle (e.g., a two-wheeled vehicle) running in a left sideward or rearward area of the vehicle. In a case where every vehicle ought to run on a right side of a road, a vehicle which is going to turn right at an intersection is also in the same situation.
To support the driver of such a vehicle which is going to turn left at an intersection, conventionally, a vehicle contact warning apparatus has been proposed (Japanese Laid-Open Patent Application No.53-27932). In this vehicle contact warning apparatus, a watching unit (including an ultrasonic sensor) watching a dead angle area in a left side of the vehicle is provided in the vehicle. When a direction indicating operation (a turn signal operation) to turn left is carried out, the driver is warned, based on information from the watching unit, that there is another vehicle in the dead angle area.
According to the conventional vehicle contact warning apparatus, when a vehicle is going to turn left at an intersection, a driver can recognize whether there is another vehicle in the dead angle area on the left side of the vehicle. Thus, the driver can drive the vehicle to turn left at the intersection without contacting another vehicle.
In the conventional vehicle contact warning apparatus, whenever there is another vehicle in the dead angle area on the left side of the vehicle, the warning is issued. For example, there is a case where the vehicle passes by another vehicle which stops on the left side of the road. In this case, while the other vehicle is in the dead angle area of the vehicle, the warning is issued. Thus, the warning is not necessarily appropriate for a driver of a vehicle which is going to turn along the roadside edge (turn left in a case where every vehicle ought to run on the left side of a road or turn right in a case where every vehicle ought to run on the right side of a road) without crossing the road at an intersection.